The invention relates to an energy generating installation comprising a gas turbine operated by steam injection, with a waste heat boiler being provided for steam production, which additionally supplies process steam to an external consumer.
Energy generating installations are known in the art, with a gas turbine being operated by additional steam injection, wherein the steam production takes place in a waste heat boiler heated by the exhaust gases of the steam turbine and a back-up firing equipment may be provided. This principle is consistently realized in the Cheng cycle where the overall steam flow can be fed into the gas turbine without a back-up firing equipment being required. Such an energy generating installation is described in the catalog "Cheng Cycle Series 7, Kraft-Warme-Kopplung mit Gas Turbinen" [Cheng Cycle Series 7, Combined heat and power generation using gas turbines] of ELIN Energieversorgung Gesellschaft mbH. As compared with steam turbine installations, the Cheng cycle is characterized by lower investment costs involved, since moderate pressures and temperates prevail in the waste heat boiler and a condenser is not required.
Further, solar steam generators are known in the art, which use solar energy for steam generating purposes. Typical installations are parabolic trough collectors where paraboloidal type reflectors focus the solar energy onto a pipe carrying a heat transfer medium. One problem encountered when using solar steam generators is the unreliable availability of solar energy. It is therefore necessary that an additional fuel-firing equipment is provided. Due to the steam conditions achievable with solar energy, the fuel fired by such a back-up equipment can only be utilized with lower energy efficiency.
In the case of hybrid installations negative interactions between solar and conventional installation sections are normally inevitable (e. g. reduced efficiency when fossil fuel is fired, restricted operating range of the solar field). Solar steam injection into a gas turbine is not attractive for pure power generation since the steam flow which can be produced in the waste heat boiler satisfies or even exceeds the maximum operating flow of the turbine. The necessity of using a 100% fossil fuel-firing back-up equipment hitherto resulted in a solar installation which had not been optimally incoporated in an overall system designed for this purpose but "placed upon" a conventional installation. The additionally generated solar heat can be utilized in such systems only to a limited extent. This reduces the utilization ratio of the solar installation and the realizable fuel saving.